Perovskite, titanite and apatite occur in jacupirangite, ijolite and nepheline syenite blocks in the tuffs and agglomerates of the active volcano Oldoinyo Lengai, N. Tanzania. In the absence of titanite, the LREE (particularly Ce) partition strongly into perovskite relative to apatite (D p e r o v / a p La 9, Ce 16, Nd 9.5), but if titanite is present the D p e r o v / a p -values are lower and erratic. In the absence of perovskite, La and Nd partition into apatite relative to titanite, whereas Ce partitions strongly into titanite. LREE partitioning between perovskite and titanite is less pronounced, particularly for Ce where D p e r o v / t i t a n i t e is only 1.7. Ba and Nb partition weakly into perovskite relative to titanite (D p e r o v / t i t a n i t e 1.5-3), whereas Zr partitions strongly into titanite (D t i t a n i t e / p e r o v ∼ 15).